Primary objectives of this work are to examine current knowledge in the field of chemical carcinogenesis and related fields and to identify criteria for the evaluation of carcinogenic effects of chemical and physical agents, for the evaluation of risk assessment methods, and for the prevention of cancer hazards in the human population. Laboratory methods and biological models for the detection and quantification of the carcinogenic activity of chemicals are examined and evaluated, with particular emphasis on animal models of carcinogenesis and in vitor models for carcinogensis studies. Quantitative biological variations among individuals, species and experimental systems indicate the need for maximal qualitative comparability of experimental models with their human pathology counterparts. An approach to carcinogenic risk evaluation was proposed on the basis of studies in a series of biological models correlated with each other in a step-by-step sequence, connecting molecular and cellular levels with the corresponding tissues, organs and organisms, both animal and human.